1. Field of the Invention
This invention pertains to heterojunction bipolar transistors (HBTs) that employ advanced antimony-based material designs.
2. Description of Related Art
Future generations of microwave and millimeter-wave radar, communications, electronic warfare, smart weapons and imaging systems will require higher precision, smaller size, increased bandwidth, lower operating voltages and lower cost of production. To meet the demand for improved high-frequency performance, considerable effort within the past ten years or so has focused on the development of GaAs-based and InP-based heterojunction bipolar transistors. As a result, a variety of HBT analog and digital circuits have been fabricated which exhibit higher gain and switching speeds with lower power dissipation. Some of the primary factors responsible for the improved HBT performance have been the use of InGaAs or GaAsSb materials in the base to improve the charge transport through the base and to lower the emitter-base and collector-base voltages needed to obtain a high collector current. As a result of these improvements, InP-based HBTs have distinct high-speed logic circuit performance advantages compared to GaAs-based HBTs and they have set records for the maximum frequency of operation for any three-terminal semiconductor device.
In the longer term, HBTs that employ InzGa1-zSb in the base and InxAl1-xAs1-xAsySb1-y or InxAl1-xPySb1-y material in the emitter along with InzGa1-zSb, or InvAl1-vAswSb1-w or InvAl1-vPwSb1-w in the collector may be more attractive than InP-based HBTs for some of the above applications due to the substantially improved electronic properties of these new material systems.